Processing of a large variety of consumer and industrial products, such as food, plastic, pharmaceutical and chemical products, usually involves one or more mixing steps for mixing component materials of the products. For accomplishing such mixing, large-capacity industrial mixers are utilized which are able to handle very large batches of material for more efficient and cost-effective mixing. One type of mixer design is referred to as a conical mixer because it utilizes a conically-shaped mixing chamber which is disposed generally vertically with respect to the ground surface. Oftentimes such conical mixers are suspended above the ground surface for more convenient discharge of the mixed material.
More specifically, conical mixers generally comprise a conically-shaped mixing chamber, an orbit arm which rotates or orbits around the inside of the chamber, and a mixing screw or auger, attached to the orbit arm, which also rotates on its own axis during the mixing process. The mixing screw is attached to the orbit arm and orbits around the chamber with the orbit arm. Simultaneously, the mixing screw rotates on a generally vertically disposed, but angled, axis. Thus, the conical mixer provides a dual mixing action, i.e., orbiting of the mixing screw around the chamber, and rotation of the mixing screw about its own axis. The mixing screw axis is usually angled to follow the angled side walls of the conically-shaped mixing chamber.
One motor driver rotates the orbit arm, while another motor driver rotates the mixing screw. The orbit arm is positioned inside of the mixing chamber and is operably mounted to orbit with the mixing screw about a centered axis. The orbit arm axis might also be offset to one side of the center of the mixing chamber as appropriate for the design of the conical mixer. The mixing screw is driven through an assembly in the orbit arm, and the main drive shaft of the mixing screw is generally centered and coaxially mounted with the main drive shaft of the orbit arm. However, since the mixing screw is positioned at the outer end of the arm, drive power must be transferred from the center cone axis to the off-center mixing screw. This is accomplished through a variety of different power transferring components including gears and shafts which are journaled in a plurality of bearing structures.
As will be appreciated, these moving gears and bearing structures require lubrication for proper operation and to prevent wear. Since the orbit arm assembly is positioned inside the mixing chamber, any contaminants from this assembly that migrate out, will be exposed to the material being mixed therein. More specifically, contaminants from the various internal moving components of the orbit arm and the lubrication oils and greases associated therewith are exposed to the mixed material through leakage from the assembly. Currently available conical mixers utilize a variety of different seals for preventing such leakage. Some conical mixers even use an elaborate fluid flow structure for directing lubricants away from openings or seams in the orbit arm assembly to prevent leakage.
While the predominant contamination associated with conical mixer orbit arms is leakage of lubricants from the orbit arm assembly, conventional conical mixers have not adequately addressed the problem. As will be appreciated, the constant orbiting of the arm and the rotation of the assembly components and the mixing screw will cause the various seals to wear and leak, whereby grease and lubricating liquid migrate through the assembly and into the conical mixing chamber thereby contaminating the mixed material. Furthermore, lubrication contaminant systems are also not entirely leak proof.
Such leakage and contamination within conical mixers is particularly a problem because of the materials mixed in such devices. Conical mixers provide low shear mixing and thus a variety of delicate products such as food and pharmaceuticals are mixed using conical mixers. Since food and pharmaceuticals are made for human consumption, even a small amount of contamination must be avoided. As mentioned, currently available conical mixers have not always adequately addressed such leakage and contamination problems.
Another problem with the leakage in the orbit arm assembly of a conical mixer is the requirement of continual maintenance of the orbit arm assembly and the mixing screw driving mechanisms. Leakage of lubricants from the orbit arm requires replacement of the lubricants and thus regularly scheduled maintenance. If such maintenance is not completed, the orbit arm assembly and the mixing screw drive components therein may prematurely wear or even seize up, thus requiring replacement of the components. Since the mixer must be inoperable during such maintenance and repair, processing delays are introduced and the efficiency and cost effectiveness of the conical mixer is thus reduced. Furthermore, the labor and material costs associated with such maintenance and repair increases the overall cost of using the conical mixer.
The problem of leakage is further exacerbated by the pressure requirements for certain mixing processes. For example, a vacuum is often required within the conical mixing chamber as a parameter for certain processes. The space within the orbit arm assembly is then maintained at a pressure higher than that within the conical mixing chamber. If the vacuum is not properly confined outside of the orbit arm assembly, the lubricants are effectively pulled out of the internal space of the orbit arm assembly to leak and contaminate the mixed material.
Accordingly, it is an objective of the present invention to address the drawbacks of the prior art conical mixers and to provide a conical mixer which reduces and eliminates contamination of the mixed material.
To that end, it is an objective of the present invention to reduce and prevent leakage of lubricants from the orbit arm assembly and from the mixing screw drive components within the mixing chamber.
It is another objective of the present invention to reduce the required maintenance for a conical mixer and to prevent failure of the orbit arm assembly and mixing screw drive components due to lubricant leakage.
It is another objective of the present invention to reduce delays associated with maintenance and repairs and thus increase the overall efficiency and cost effectiveness of a conical mixer and to thus reduce the maintenance and operational costs of utilizing a conical mixer.